Patellar Dislocation/Subluxation

Malalignments of the patellofemoral (PF) joint, such as recurrent patellar dislocation/subluxation, habitual patellar dislocation, and permanent patellar dislocation, cause uneven and excessive loading on the PFJ and result in PF osteoarthritis (OA) and potentially lead to femorotibial (FT) OA. Such patients often exhibit anatomical variations, such as trochlea dysplasia and valgus knee, which are predisposing factors for dislocation (Table 79.1). The anatomy of patients with PF-OA differs significantly from that of patients with medial OA, which is more common in Japan. Therefore, special caution should be taken during their surgeries.